1. Technical Field
The present disclosure relates to the field of LED technologies, and more particularly, to a light emitting diode (LED) dimming drive device, an LED dimming drive method and a liquid crystal display (LCD).
2. Description of Related Art
With continuous advancement of the liquid crystal display (LCD) technologies, more and more manufacturers now choose to use light emitting diodes (LEDs) as backlight sources in LCD panels. Use of LEDs as backlight sources in LCD panels provides a lot of advantages; for example, the LCD panels can be made to have a smaller size, a longer service life, a shorter response time, a lower power consumption and much better color performance than the conventional cold cathode fluorescent lamps (CCFLs).
As the LED technologies advance continuously, requirements on dimming performance of LEDs become increasingly stricter. In the conventional LED dimming drive devices, generally a pulse width modulation (PWM) signal is output to each of a plurality of dimming control circuits simultaneously, so as to control the dimming control circuits simultaneously. In practical implementations, the LEDs are turned on or off by using the PWM signal to control a dimmer switch in each of the dimming control circuit to be turned on or off, and the dimmer switch may be implemented by a metal-oxide-semiconductor (MOS) transistor.
Hereinafter, one dimming control circuit will be taken as an example to illustrate a dimming process in the prior art. When a PWM signal inputted into a certain dimming control circuit is at a high level, the dimmer switch in the dimming control circuit will be turned on by the high-level PWM signal to switch on an LED which connected with the dimming control circuit; conversely, when the PWM signal is at a low level, the dimmer switch in the dimming control circuit is turned off by the low-level PWM signal so as to switch off the LED which connected with the dimming control circuit.
However, in the prior art, LEDs in all LED paths are switched on simultaneously, so a large amount of energy must be provided for the whole LED light emitting system within a short time. This may cause loud noises and strong electromagnetic interferences (EMI) and even instable operation of the PWM power supply system.